Transfer printing processes are known in the art, whereby a decor film is brought into intimate contact with a motif carrier for the transfer of the motif image onto the decor film. The motif carrier carries or contains the motif image in the form of organic dispersive dyes. The pressure needed for the transfer is applied through a structured mat, whereby pressure and heat are supplied simultaneously for the transfer of the motif by diffusion of the dyes onto the decor film.
The application of the above method has encountered problems when the decor film on which the image motif is to be printed, has a structured surface. By "structured surface" is meant a textured surface having ridges and valleys which is the case, for example, for imitation leather-type surfaces or grained surfaces. Materials with such surfaces are used for decorating purposes on the interior structural components of aircraft cabins to form flat and curved surface components. Such covering materials are produced as films having a layered structure with a cover layer made, for example, of a polyvinyl fluoride. Lightweight composite panels made of fiber reinforced synthetic materials are used for this purpose and covered with the above mentioned films. Depending on the final application,the panels may have a plane or curved configuration.
For decorative purposes the films also referred to as decor films, having the above mentioned structured surface, can be printed with images by screen printing processes. Due to the limitations inherent in such screen printing processes it is basically possible only to produce single or multi-color line motifs. An application of, for example, photographically recorded images or motifs on the respective films is not possible by screen printing processes. However, it is known to transfer such photographically recorded image motifs by means of the transfer printing process. This process, however, has been limited heretofore to smooth surfaces, for example, acrylic glass plates.
European Patent Publication (EP) 0,110,220 A2 shows a respective method for transfer printing on solid objects of synthetic material or on objects covered with a surface coating of lacquer or synthetic material. The transfer printing uses a surface area dye carrier, whereby the dye transfer takes place at a suitable temperature while pressing the dye carrier onto the surface of the object to be printed. The printing pressure on the surface area dye carrier is accomplished by a gas pressure in excess of the atmospheric pressure, and the surface to be printed is kept at a temperature below the thermoplastic range of the material to be printed. This known method of transfer printing makes sure that the originally glossy surface of an object to be printed is retained even after the printing. This retaining of the glossy surface is enhanced by utilizing the characteristic of certain types of acrylic glass. This characteristic is the ability to assume a thermo-elastic state without entering into a thermoplastic state. Additionally, certain measures are taken in order to contact the dye or motif carrier with the object to be printed only for a short duration. The just mentioned European Publication also teaches the use of a felt cloth in those instances where it is intended to obtain a mat finish as a result of the printing on the initially glossy printed surface. The felt cloth thus embosses the printed surface which was originally smooth and glossy to obtain a mat surface.
German Patent Publication (DE-OS) 2,731,121 illustrates a method for producing prints on surfaces of formed bodies of thermoplastic synthetic materials by means of dispersion dyes without any bonding agents. In this known method the dyes are first applied to an intermediate carrier by means of conventional printing techniques. The so-prepared intermediate carrier is then pressed onto the surface to be printed while simultaneously heating the surface of the formed body to a temperature sufficient for a sublimation and diffusion of the dyes. This known method makes it possible to print on formed bodies of thermoplastic synthetic materials, for example liquid containers, without destroying the shape of these formed bodies due to the temperatures that are necessary for performing the known transfer printing.
It is also known to transfer a photographic image onto a film of, for example, polycarbonate by a diffusion transfer and to then adhesively bond such film onto a surface such as a panel, for example, a door panel. This known method, however, is not suitable for transferring a photographic image motif onto a synthetic material film which has already a structured, textured surface rather than a smooth surface.